Assessment of peach internal flesh browning through colorimetric measures

• ΔL* is the best CIELAB parameter for describing internal flesh browning objectively.
• ΔL* = 4.7 is the threshold of internal flesh browning perceived by the panel.
• Four categories of internal flesh browning of peach were developed based on ΔL*.

The purpose of this trial was to develop an objective internal flesh browning (IFB) assessment methodology for fresh peach. Six peach and three nectarine cultivars were used in this research. The fruit was maintained at 4 °C for 21 and 31 days. They were then evaluated after three additional days of maintenance at 20 °C. The differences in the CIELAB color parameters of the flesh ΔL*, ΔE*, Δh°*, ΔC*, Δa*, and Δb* were then assessed. ΔL* were assessed with both fresh fruit and fruit after postharvest treatments; after regression analysis, this resulted in the best CIELAB parameter to describe IFB. A trained sensory panel was used to corroborate the results. Between ΔL* and the panel assessment of IFB, was obtained the highest determination coefficient (R2 = 0.84). Furthermore, through a triangular test, it was determined that ΔL* = 4.7 corresponds to the IFB peach flesh threshold, as perceived by the panel. Afterward, through a regression tree, four IFB categories were defined: (1) no IFB symptoms, when ΔL* < 4.7; (2) incipient IFB symptoms, when 4.7 ≤ ΔL* < 8.0; (3) severe IFB symptoms, when 8.0 ≤ ΔL* < 21; and (4) extreme IFB symptoms, when ΔL* ≥ 21. We recommend the use of ΔL* when objective phenotyping of IFB of peach flesh is required.